The Laws of Conservation of Mass & Indestructibility of Matter ... - Free Printable

Let’s go step by step to solve each part of the worksheet.

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First, look at the reaction:

CH₄ + O₂ → CO₂ + H₂O

We’re told:
- Carbon = gray
- Hydrogen = blue
- Oxygen = red

Now let’s count atoms on each side.

Reactants (left side):
- CH₄ has 1 carbon and 4 hydrogens.
- O₂ has 2 oxygens.
→ So total reactants:
Carbon = 1
Hydrogen = 4
Oxygen = 2

Products (right side):
- CO₂ has 1 carbon and 2 oxygens.
- H₂O has 2 hydrogens and 1 oxygen.
→ So total products:
Carbon = 1
Hydrogen = 2
Oxygen = 3 (2 from CO₂ + 1 from H₂O)

Wait — that doesn’t match! Reactants have 4 H and 2 O, but products have only 2 H and 3 O. That means this equation is not balanced.

But the question asks us to fill in the table based on what’s shown — not whether it’s balanced yet.

So for the table:

Reactants:
Carbon = 1
Hydrogen = 4
Oxygen = 2

Products:
Carbon = 1
Hydrogen = 2
Oxygen = 3

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Question 9: Does this represent the law of conservation of mass?

The law says: Matter cannot be created or destroyed in a chemical reaction. So the number of each type of atom must be the same on both sides.

Here, we have:
- Same carbon (1=1) ✔
- Different hydrogen (4 vs 2) ✘
- Different oxygen (2 vs 3) ✘

So NO — it does NOT follow the law because atoms are not conserved. The model as drawn is unbalanced.

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Next reaction: Al₂O₃ → Al + O₂

Count atoms:

Left (reactant):
Al₂O₃ → 2 aluminum, 3 oxygen

Right (products):
Al → 1 aluminum
O₂ → 2 oxygen
Total right: 1 Al, 2 O

Compare:
- Aluminum: 2 vs 1 → not equal ✘
- Oxygen: 3 vs 2 → not equal ✘

So again, atoms are not conserved.

Question 10: Does this demonstrate the law?

NO — because the number of aluminum and oxygen atoms changed. You can’t lose atoms in a real chemical reaction. This equation is unbalanced.

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Last reaction: Visual model

Left side:
- Two molecules of H₂ (each has 2 white balls → so 4 white balls total)
- One molecule of O₂ (two red balls → 2 red balls)

Right side:
- Two molecules of H₂O (each has 2 white + 1 red → so 4 white + 2 red total)

Count:

Reactants:
Hydrogen (white) = 4
Oxygen (red) = 2

Products:
Hydrogen (white) = 4
Oxygen (red) = 2

They match!

Question 11: Does this demonstrate the law?

YES — because the number of each kind of atom is the same before and after. No atoms were lost or gained. This follows the law of conservation of mass.

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Final Answer:

Table:

Reactants:
Carbon = 1
Hydrogen = 4
Oxygen = 2

Products:
Carbon = 1
Hydrogen = 2
Oxygen = 3

Question 9:
No, because the number of hydrogen and oxygen atoms is different on each side. Atoms must be equal for the law to hold.

Question 10:
No, because there are 2 aluminum and 3 oxygen atoms on the left, but only 1 aluminum and 2 oxygen atoms on the right. Atoms are not conserved.

Question 11:
Yes, because there are 4 hydrogen atoms and 2 oxygen atoms on both sides. The atoms are just rearranged, not created or destroyed.